Cytokines, in general, are important signaling molecules that are essential to immune and inflammatory responses in mammals. Interleukin-1β and IL-18 are key components of the cytokine network. IL-1β stimulates the production of Tumor Necrosis Factor-α (TNF-α), and the combined action of IL-1β, IL-18 and TNF-α induces further cytokine production, chemokine production, expression of cellular adhesion molecules, and increased vascular permeability. In addition, IL-1β stimulates fibroblast differentiation and proliferation, the production of prostaglandins, collagenase and phospholipase by synovial cell and chondrocytes, basophil and eosinophil degranulation, and neutrophil activation. These mediators contribute to autoimmune and inflammatory disorders in many organ systems.
IL-1β possesses diverse biological effects contributing to the pathogenesis of acute and chronic inflammatory and autoimmune diseases (C A Dinarello, Blood, (1996) 87, 2095). For example, Il-1β contributes to disease progression in rheumatoid arthritis and osteoarthritis, where it mediates inflammatory symptoms, contributes to the destruction of cartilage proteoglycan, and also contributes to bone loss in afflicted joints. IL-1β overexpression also contributes to disease progression in atherosclerosis by regulating the expression and activation of matrix metalloproteases. Other conditions where IL-1β plays a major role in pathogenesis include sepsis syndrome, inflammatory bowel syndrome, acute and chronic myelogenous leukemia, insulin-dependent diabetes mellitus, osteoporosis, and periodontal disease.
The caspases are a family of structurally similar, intracellular cysteine proteases that play an important role in cytokine maturation and apoptosis. Caspase-1 (interleukin-1β converting enzyme, ICE) is primarily responsible for key steps in immunity and the inflammatory response since it catalyzes the proteolytic cleavage of the pro-inflammatory cytokines pro-IL-1β and pro-IL-18 to the bioactive forms IL-1β and IL-18. Since IL-1β triggers a multitude of biological responses and is implicated in the pathogenesis of many inflammatory diseases, as outlined above, the inhibition of ICE is a recognized target for therapeutic intervention. Therefore, ICE inhibitors have utility for the treatment of inflammatory diseases and autoimmune diseases, such as RA and OA. In addition, other caspases and related homologs of ICE appear to be involved regulating biological processes such as apoptosis. Therefore, inhibition of caspases also provides a recognized therapeutic approach for treating additional pathological conditions. Diseases where caspase inhibitors can provide theraputic utility include neurodegenerative diseases (such as Alzheimer's, Huntington's, and Parkinson's diseases), ischemia, stroke, and trauma.
There is therefore a long felt need in the art for pharmaceutical compositions which comprise novel active ingredients for reversibly or irreversibly inhibiting Caspase enzymes resulting in the treatment of pathological conditions and diseases described further herein, inter alia, inflammation of joints and other forms of synovial tissue associated with osteoarthritis and rheumatoid arthritis, Huntington's Disease, Alzheimer's disease, neuronal death, brain, intestinal or mycardial ischemia, repurfusion injury, endotoxic shock, amyotrophic lateral sclerosis, multiple sclerosis, atherosclerosis, hepatitis, inflammatory bowel syndrome, shigellosis, meningitis, sepsis, acute and chronic myelogenous leukemia, insulin-dependent diabetes mellitus, osteoporosis, and periodontal disease. Each of these disease states involves cytokine activity, which can be abated, controlled or otherwise mediated by the limiting or stopping the activity of one or more Caspase enzymes.